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-rw-r--r--tools/testing/selftests/rseq/rseq.h9
1 files changed, 8 insertions, 1 deletions
diff --git a/tools/testing/selftests/rseq/rseq.h b/tools/testing/selftests/rseq/rseq.h
index 4e217b620e0c..062d10925a10 100644
--- a/tools/testing/selftests/rseq/rseq.h
+++ b/tools/testing/selftests/rseq/rseq.h
@@ -60,7 +60,14 @@
extern ptrdiff_t rseq_offset;
/*
- * Size of the registered rseq area. 0 if the registration was
+ * The rseq ABI is composed of extensible feature fields. The extensions
+ * are done by appending additional fields at the end of the structure.
+ * The rseq_size defines the size of the active feature set which can be
+ * used by the application for the current rseq registration. Features
+ * starting at offset >= rseq_size are inactive and should not be used.
+ *
+ * The rseq_size is the intersection between the available allocation
+ * size for the rseq area and the feature size supported by the kernel.
* unsuccessful.
*/
extern unsigned int rseq_size;